The article investigates features of the functional cerebral activity formation in preterm infants with extreme low and very low birth weight with severe and moderate hypoxic-ischemic encephalopathy. The article shows that preterm infants with more severe hypoxic-ischemic encephalopathy still have the delay in formation of functional cerebral activity to the gestational age of 44-46 weeks. This fact can testify disturbances of synaptogenesis and of systemic relations among the parts of the brain.